Methods and apparatuses for dynamic transmit diversity fallback

ABSTRACT

Systems, methods, apparatuses, and computer program products for dynamic transmit diversity fallback are provided. One method may include configuring a user equipment with a maximum number of multiple-input multiple-output (MIMO) layers used for transmission mode 9 or transmission mode 10 scheduling, and performing, by a network node, at least one of transmission mode 9 or transmission mode 10 scheduling. The configuring may include indicating to the user equipment to use a modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional patentapplication No. 62/710,293 filed on Feb. 16, 2018. The contents of thisearlier filed application are hereby incorporated by reference in theirentirety.

FIELD

Some example embodiments may generally relate to mobile or wirelesstelecommunication systems. For instance, various example embodiments mayrelate to dynamic transmit diversity in such telecommunication systems.

BACKGROUND

Examples of mobile or wireless telecommunication systems may include theUniversal Mobile Telecommunications System (UMTS) Terrestrial RadioAccess Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN(E-UTRAN), LTE-Advanced (LTE-A), LTE-A Pro, and/or fifth generation (5G)radio access technology or new radio (NR) access technology. Fifthgeneration (5G) or new radio (NR) wireless systems refer to the nextgeneration (NG) of radio systems and network architecture. It isestimated that NR will provide bitrates on the order of 10-20 Gbit/s orhigher, and will support at least enhanced mobile broadband (eMBB) andultra-reliable low-latency-communication (URLLC). NR is expected todeliver extreme broadband and ultra-robust, low latency connectivity andmassive networking to support the Internet of Things (IoT). With IoT andmachine-to-machine (M2M) communication becoming more widespread, therewill be a growing need for networks that meet the needs of lower power,low data rate, and long battery life. It is noted that, in 5G or NR, thenodes that can provide radio access functionality to a user equipment(i.e., similar to Node B in E-UTRAN or eNB in LTE) may be referred to asa next generation or 5G Node B (gNB).

SUMMARY

One embodiment is directed to a method that may include configuring auser equipment with a maximum number of multiple-input multiple-output(MIMO) layers used for transmission mode 9 or transmission mode 10scheduling, and performing, by a network node, at least one oftransmission mode 9 or transmission mode 10 scheduling. The configuringmay include indicating to the user equipment to use a modified mappingtable providing transmit diversity fallback for the at least one oftransmission mode 9 or transmission mode 10 scheduling.

Another embodiment is directed to an apparatus that may include at leastone processor and at least one memory comprising computer program code.The at least one memory and computer program code may be configured,with the at least one processor, to cause the apparatus at least toconfigure a user equipment with a maximum number of multiple-inputmultiple-output (MIMO) layers used for transmission mode 9 ortransmission mode 10 scheduling, and perform at least one oftransmission mode 9 or transmission mode 10 scheduling. The configuringmay include indicating to the user equipment to use a modified mappingtable providing transmit diversity fallback for the at least one oftransmission mode 9 or transmission mode 10 scheduling.

Another embodiment is directed to an apparatus that may includeconfiguring means for configuring a user equipment with a maximum numberof multiple-input multiple-output (MIMO) layers used for transmissionmode 9 or transmission mode 10 scheduling, and performing means forperforming at least one of transmission mode 9 or transmission mode 10scheduling. The configuring means may include means for indicating tothe user equipment to use a modified mapping table providing transmitdiversity fallback for the at least one of transmission mode 9 ortransmission mode 10 scheduling.

Another embodiment is directed to a method that may include receiving,from a network node, a configuration of a maximum number ofmultiple-input multiple-output (MIMO) layers used for transmission mode9 or transmission mode 10 scheduling, and using, based on the receivedconfiguration, a modified mapping table providing transmit diversityfallback for at least one of transmission mode 9 or transmission mode 10downlink shared channel reception.

Another embodiment is directed to an apparatus that may include at leastone processor and at least one memory comprising computer program code.The at least one memory and computer program code may be configured,with the at least one processor, to cause the apparatus at least toreceive, from a network node, a configuration of a maximum number ofmultiple-input multiple-output (MIMO) layers used for transmission mode9 or transmission mode 10 scheduling, and use, based on the receivedconfiguration, a modified mapping table providing transmit diversityfallback for at least one of transmission mode 9 or transmission mode 10downlink shared channel reception.

Another embodiment is directed to an apparatus that may includereceiving means for receiving, from a network node, a configuration of amaximum number of multiple-input multiple-output (MIMO) layers used fortransmission mode 9 or transmission mode 10 scheduling, and using meansfor using, based on the received configuration, a modified mapping tableproviding transmit diversity fallback for at least one of transmissionmode 9 or transmission mode 10 downlink shared channel reception.

BRIEF DESCRIPTION OF THE DRAWINGS

For proper understanding of the invention, reference should be made tothe accompanying drawings, wherein:

FIG. 1a illustrates an example flow diagram of a method, according to anembodiment;

FIG. 1b illustrates an example flow diagram of a method, according toanother embodiment;

FIG. 2a illustrates an example block diagram of an apparatus, accordingto an embodiment; and

FIG. 2b illustrates an example block diagram of an apparatus, accordingto another embodiment.

DETAILED DESCRIPTION

It will be readily understood that the components of certain exampleembodiments, as generally described and illustrated in the figuresherein, may be arranged and designed in a wide variety of differentconfigurations. Thus, the following detailed description of some exampleembodiments of systems, methods, apparatuses, and computer programproducts for dynamic transmit diversity fallback, as represented in theattached figures and described below, is not intended to limit the scopeof certain embodiments but is representative of selected exampleembodiments.

The features, structures, or characteristics of example embodimentsdescribed throughout this specification may be combined in any suitablemanner in one or more embodiments. For example, the usage of the phrases“certain embodiments,” “some embodiments,” or other similar language,throughout this specification refers to the fact that a particularfeature, structure, or characteristic described in connection with anembodiment may be included in at least one embodiment. Thus, appearancesof the phrases “in certain embodiments,” “in some embodiments,” “inother embodiments,” or other similar language, throughout thisspecification do not necessarily all refer to the same group ofembodiments, and the described features, structures, or characteristicsmay be combined in any suitable manner in one or more embodiments.

Additionally, if desired, the different functions or steps discussedbelow may be performed in a different order and/or concurrently witheach other. Furthermore, if desired, one or more of the describedfunctions or steps may be optional or may be combined. As such, thefollowing description should be considered as merely illustrative of theprinciples and teachings of certain example embodiments, and not inlimitation thereof.

For shorter transmission time interval (TTI) physical downlink sharedchannel (PDSCH) operation, there is currently no transmit diversityfallback scheduling possible for PDSCH with transmission mode (TM) 9and/or TM 10, as is the case for LTE 1 ms TTI. As will be discussed indetail below, certain embodiments provide methods to enable dynamicfallback to transmit diversity with shorter TTI PDSCH TM9 and TM10.

For 1 ms TTI LTE operation, a UE configured with TM9 or TM10 will, inaddition to the downlink control information (DCI) format scheduling TM9(DCI Format 2C) and TM10 (DCI Format 2D), also monitor for DCI Format1A, which enables dynamic fallback to diversity transmission. This maybe beneficial, for example, in cases where there is no accurate channelstate information (CSI) available or concerning high reliabilitytransmissions requiring diversity.

In contrast, for shorter TTI PDSCH there is no transmission diversityfallback available through DCI, as the UE for shorter TTI PDSCHscheduling would only monitor for a single DL DCI format schedulingshorter TTI PDSCH. This can be seen from Table 1 shown below (whichcorresponds to Table 7.1-5C in 3GPP TS 36.213 V15.0.0).

TABLE 1 Transmission Transmission scheme of PDSCH mode DCI format SearchSpace corresponding to SPDCCH Mode 1 DCI format 7- UE specific by C-RNTISingle-antenna port, port 0 (see Subclause 1A 7.1.1) Mode 2 DCI format7- UE specific by C-RNTI Transmit diversity (see Subclause 7.1.2) 1AMode 3 DCI format 7- UE specific by C-RNTI Large delay CDD (seeSubclause 7.1.3) 1B Mode 4 DCI format 7- UE specific by C-RNTIClosed-loop spatial multiplexing (see Subclause 1C 7.1.4) Mode 6 DCIformat 7- UE specific by C-RNTI Closed-loop spatial multiplexing (seeSubclause 1D 7.1.4) using a single transmission layer Mode 8 DCI format7- UE specific by C-RNTI Dual layer transmission, port 7 and 8 (see 1ESubclause 7.1.5A) or single-antenna port, port 7 or 8 (see Subclause7.1.1) Mode 9 DCI format 7- UE specific by C-RNTI Dual layertransmission port 7-8 (see Subclause 1F 7.1.5A), if UE is configuredwith higher layer parameter semiOpenLoop, up to 4 layer transmission,ports 7-10 (see Subclause 7.1.5B) otherwise; or single-antenna port,port 7, 8, 11, or 13 (see Subclause 7.1.1) if UE is configured withhigher layer parameter dmrs-tableAlt, single-antenna port, port 7 or 8(see Subclause 7.1.1) otherwise Mode 10 DCI format 7- UE specific byC-RNTI Dual layer transmission port 7-8 (see Subclause 1G 7.1.5A), if UEis configured with higher layer parameter semiOpenLoop, up to 4 layertransmission, ports 7-10 (see Subclause 7.1.5B) otherwise; orsingle-antenna port, port 7, 8, 11, or 13 (see Subclause 7.1.1) if UE isconfigured with higher layer parameter dmrs-tableAlt, single-antennaport, port 7 or 8 (see Subclause 7.1.1) otherwise

Certain example embodiments provide a solution for how to enabletransmit diversity fallback for TM9 and TM10, without any neededadditional bits. Dynamic transmit diversity fallback within the DCI canbe done if there are unused signalling states or bits available in theprecoding signaling. In this case, transmit diversity fallback may beachieved by utilizing the unused states, for example as done for shorterTTI DL TM4 with the precoding indication as shown in Table 2(corresponding to Table 5.3.3.1.19-1 of 3GPP TS 36.212 V15.0.1) andTable 3 (corresponding to Table 5.3.3.1.19-2 of 3GPP TS 36.212 V15.0.1)below.

TABLE 2 Bit field mapped to index Message 0 2 layers: Transmit diversity1 1 layer: Precoding corresponding to precoding vector [1 1]^(T) /{square root over (2)} 2 1 layer: Precoding corresponding to precodervector [1 −1]^(T) / {square root over (2)} 3 1 layer: Precodingcorresponding to precoder vector [1 j]^(T) / {square root over (2)} 4 1layer: Precoding corresponding to precoder vector [1 −j]^(T) / {squareroot over (2)} 5 1 layer: Precoding according to the latest PMI reporton PUSCH, using the precoder(s) indicated by the reported PMI(s), if RI= 2 was reported, using 1^(st) column multiplied by {square root over(2)} of all precoders implied by the reported PMI(s) 6 1 layer:Precoding according to the latest PMI report on PUSCH, using theprecoder(s) indicated by the reported PMI(s), if RI = 2 was reported,using 2^(nd) column multiplied by {square root over (2)} of allprecoders implied by the reported PMI(s) 7 2 layers: Precodingcorresponding to precoder${matrix}\mspace{14mu}{\frac{1}{2}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}}$ 8 2 layers: Precoding corresponding to precoder${matrix}\mspace{14mu}{\frac{1}{2}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}}$ 9 2 layers: Precoding according to the latest PMI reporton PUSCH, using the precoder(s) indicated by the reported PMI(s) 10~15reserved

TABLE 3 Bit field mapped to index Message 0 4 layers: Transmit diversity1 1 layer: TPMI = 0 2 1 layer: TPMI = 1 . . . . . . 16 1 layer: TPMI =15 17 1 layer: Precoding according to the latest PMI report on PUSCHusing the precoder(s) indicated by the reported PMI(s) 18 2 layers: TPMI= 0 19 2 layers: TPMI = 1 . . . . . . 33 2 layers: TPMI = 15 34 2layers: Precoding according to the latest PMI report on PUSCH using theprecoder(s) indicated by the reported PMI(s) 35 3 layers: TPMI = 0 36 3layers: TPMI = 1 . . . . . . 50 3 layers: TPMI = 15 51 3 layers:Precoding according to the latest PMI report on PUSCH using theprecoder(s) indicated by the reported PMI(s) 52 4 layers: TPMI = 0 53 4layers: TPMI = 1 . . . 67 4 layers: TPMI = 15 68 4 layers: Precodingaccording to the latest PMI report on PUSCH using the precoder(s)indicated by the reported PMI(s) 69~127 reserved

A similar approach may also be taken for the DCIs scheduling DL TM6 (DCIFormat 7-1D) as well as for DL TM8 (DCI Format 7-1D), where there is areserved value available also, as shown Table 4 below (corresponding toTable 5.3.3.1.21-1 of 3GPP TS 36.212 V15.0.1).

TABLE 4 Number of layers and antenna port field value Number of layersAntenna port 00 1 7 01 1 8 10 2 7, 8 11 Reserved Reserved

In contrast, however, for DL TM9 and TM10, all the signalling states arealready being used. Table 5 (corresponding to Table 5.3.3.1.22-1 of 3GPPTS 36.212 V15.0.1) shows the antenna port(s), scrambling identity andnumber of layers for TM9 (and TM10). As specified in Table 5, in whichthere are 3 bits where n_(SCID) is the scrambling identity for antennaports 7 and 8, or 1 bit as specified where n_(SCID) is the scramblingidentity for antenna ports 7 and 8 when higher layer parametersemiOpenLoop is configured. When higher layer parameter semiOpenLoop isconfigured, antenna ports 7 and 8 may be used for transmit diversity.Accordingly, a solution is needed to enable transmit diversity fallbackfor TM9 and TM10, using just the 3 bits/8 states available (i.e.,without any additional bits).

TABLE 5 Value Message 0 1 layer, port 7, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 2 1 layer, port 8, n_(SCID) = 0 3 1 layer, port 8, n_(SCID)= 1 4 2 layers, ports 7-8, n_(SCID) = 0 5 2 layers, ports 7-8, n_(SCID)= 1 6 3 layers, ports 7-9 7 4 layers, ports 7-10

It is noted that transmit diversity for TM9 and TM10 can be higher layerconfigured by using the RRC parameter semiOpenLoop, where transmitdiversity utilizes antenna port 7 and port 8 using the n_(SCID) definedby the one bit signalling. However, in this case, only transmitdiversity can be used but not scheduling higher order downlink (DL)multiple-input multiple-output (MIMO) or transmit diversity dynamically.

As mentioned above, one embodiment may enable dynamic fallback indicatedin the scheduling DCI for DL TM9 (DCI Format 7-1F) and TM10 (DCI Format7-1G) for shorter TTI, without increasing the DCI signalling overhead.In other words, an embodiment is configured to use just the 3 availablebits Antenna port(s), scrambling identity and number of layersindication, to enable dynamic transmit diversity fallback.

According to some examples, a UE may have support for up to 2DL MIMOlayers or support for up to 4 DL MIMO layers for LTE shorter TTI (slot-or subslot) PDSCH. Certain embodiments may provide solutions for both ofthese scenarios.

For the case where the UE supports up to 2 DL MIMO layers, looking atTable 5 above the last two entries (i.e., 3 or 4 layer spatialmultiplexing) will actually never be used in the DCI signalling, as theUE would only support PDSCH TM9 or TM10 reception with up to 2 MIMOlayers anyhow. Thus, an embodiment defines an alternative table (Table6) for the case where only up to 2 spatially multiplexed MIMO layers aresupported for shorter TTI TM9 and/or TM10. As shown in Table 6 below,the two non-useable entries (3 & 4 layers MIMO) are replaced by atransmit diversity solution supported with semiOpenLoop TM9 and TM10operation. In certain embodiments, this could be done by having adifferent table depending on the number of supported MIMO layers in thecommunication. For example, in the case of the UE supporting only up to2 layers, the mapping table that is used can be Table 6.

TABLE 6 Value Message 0 1 layer, port 7, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 2 1 layer, port 8, n_(SCID) = 0 3 1 layer, port 8, n_(SCID)= 1 4 2 layers, ports 7-8, n_(SCID) = 0 5 2 layers, ports 7-8, n_(SCID)= 1 6  

  2 layers, transmit diversity ports 7-8, n_(SCID) = 0 7  

  2 layers, transmit diversity ports 7-8, n_(SCID) = 1

In some embodiments, at least for UEs supporting up to 2 spatiallymultiplexed layers or operation restricted to up to 2 MIMO layers, thedynamic transmit diversity fallback may be done without having anyeffect on the scheduling flexibility. Certain example embodimentsprovide different options on how to define when the up to 2 MIMO layersare used. These options may include UE indication based or eNBindication based.

For the UE indication based option, a UE may report its MIMO capabilityindependently for shorter TTI. According to certain embodiments, in thecase where the UE reports support for only up to 2 layer MIMO, Table 6discussed above may be used instead of the table specified in thecurrent 3GPP specifications. It is noted that Table 6 is just oneexample embodiment, which may be modified according to other exampleembodiments. As an example, in certain embodiments, the order of therows or entries shown in Table 6 may be modified. For instance, the newentries related to transmit diversity may be placed on the lowestvalues, e.g., row with “value 0” and/or “value 1”, etc., while the other“older” entries could be moved down. In other embodiments, the newtransmit diversity entries may be moved up to any of the rows of thetable.

For the eNB indication based option, in one embodiment, there may beprovided RRC configuration on the maximum number of MIMO layers. Forexample, an embodiment may use the RRC signaling maxLayersMIMO or asimilar new shorter TTI specific RRC signaling on the maximum number oflayers used.

Another embodiment of the eNB indication option may be based on codebooksubset restriction. The shorter TTI PDSCH operation supports a ratherextensive flexibility in the codebook subset restriction for CSIreporting (restriction of the PMI/Rank combinations that the UE isallowed to indicate to the eNB). Therefore, in this embodiment, in caseonly codebooks for up to 2 layers are to be supported (which basicallyrestricts the rank for CSI reporting), the support for only up to 2layers and usage of Table 6 above may be assumed.

Another embodiment of the eNB indication option may be limited by thenumber of configured channel state information reference signal (CSI-RS)ports, which already now limits the rank in the CSI reporting. In thisexample, if only two CSI-RS ports are configured, then the UE may assumeuse of Table 6.

Another embodiment of the eNB indication option may include dedicatedRRC configuration of using Table 6. This example having a dedicatedconfiguration of the table to be applied, the table supporting up to 4layer MIMO spatial multiplexing or Table 6 with up to 2 layers+transmitdiversity fallback.

Furthermore, it should also be noted that additional transmit diversitysolutions can be envisioned to be signalled according to exampleembodiments. These may include, for example, 4 layer transmit diversitywith ports 7-10 or CRS-based TX diversity fallback, as shown in theexamples of Table 7 and Table 8 shown below.

TABLE 7 Value Message 0 1 layer, port 7, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 2 1 layer, port 8, n_(SCID) = 0 3 1 layer, port 8, n_(SCID)= 1 4 2 layers, ports 7-8, n_(SCID) = 0 5 2 layers, ports 7-8, n_(SCID)= 1 6 2 layers, transmit diversity ports 7-8, n_(SCID) = 0 7 4 layers,transmit diversity ports 7-10

TABLE 8 Value Message 0 1 layer, port 7, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 2 1 layer, port 8, n_(SCID) = 0 3 1 layer, port 8, n_(SCID)= 1 4 2 layers, ports 7-8, n_(SCID) = 0 5 2 layers, ports 7-8, n_(SCID)= 1 6 2 layers, transmit diversity ports 7-8, n_(SCID) = 0 7 Transmitdiversity based on CRS

For the case where the UE supports up to 4 DL MIMO layers, there is nospace in the dynamic signaling as all the elements for up to 4 DL MIMOlayers are already used. According to an embodiment, Table 9 shown belowmay be used as the mapping table.

TABLE 9 Value Message 0 1 layer, port 7, n_(SCID) = 0 1 1 layer, port 7,n_(SCID) = 1 2 1 layer, port 8, n_(SCID) = 0 3 1 layer, port 8, n_(SCID)= 1 4 2 layers, ports 7-8, n_(SCID) = 0 5  

  2 layers, transmit diversity, ports 7-8, n_(SCID) = 1 6 3 layers,ports 7-9 7 4 layers, ports 7-10

With the change provided in Table 9, the multi-user MIMO operation mightslightly deviate for the UE with spatial multiplexing, but would stillbe enabled and supported by multi-user MIMO multiplexing of transmitdiversity for one UE with up to 2 layer MIMO of other UE(s). Therefore,in one embodiment, the current mapping table may be changed as noted inTable 9 and only this table is supported for up to 4 layer MIMO. Inanother embodiment, the new Table 9 for up to 4 layers can be configuredby dedicated RRC signaling, instead of the current table in the 3GPPspecifications.

It is noted that Tables 7, 8, and 9 shown above illustrate some possibleexample embodiments, which may be modified according to other exampleembodiments. For example, in certain embodiments, the order of the rowsor entries shown in Tables 7, 8, and/or 9 may be modified. For instance,the new entries related to transmit diversity may be placed on thelowest values, e.g., row with “value 0” and/or “value 1”, etc., whilethe other “older” entries could be moved down. In other embodiments, thenew transmit diversity entries may be moved up to any of the rows of thetable.

In view of the above, in an embodiment from the perspective of the eNBin case of support for up to 2 layers, the eNB may optionally configurea UE with a maximum of 2 MIMO layers for TM9 and/or TM10 (if based oneNB configuration). According to certain embodiments, the configurationmay be a dedicated configuration of maximum MIMO layers (in general orspecifically for shorter TTI), may depend on number of CSI-RS ports(e.g., only two CSI RS ports are configured), and/or may be throughcodebook subset restriction (e.g., UE is configured not to reportrank>2).

In an embodiment, the eNB may receive a report from the UE of themaximum number of MIMO layers supported. According to some embodiments,if the maximum number of supported layers is 2, then the eNB may use, orindicate the UE to use, Table 6 or Table 7 or Table 8 for TM9 and/orTM10 scheduling for up to 2 layers, thereby enabling dynamic fallback.According to some other embodiments, if the maximum number of supportedlayers is greater than 2, then the eNB may use, or indicate the UE touse, Table 9 for TM9 and/or TM10 scheduling for up to 4 layers (legacy,or modified table 9 as noted above).

In an embodiment from the perspective of the UE in case of support forup to 2 layers, the UE may be configured to report the maximum number ofMIMO layers supported to an eNB based on UE capability signaling.Optionally, in one embodiment, the UE may receive eNB configuration of amaximum of 2 MIMO layers for TM9 and/or TM10 (if based on eNBconfiguration). For example, according to some embodiments, theconfiguration may be a dedicated configuration of maximum MIMO layers(in general or specifically for shorter TTI), may depend on number ofCSI-RS ports (e.g., only two CSI RS ports are configured), and/or may bethrough codebook subset restriction (e.g., UE is configured not toreport rank>2).

According to an embodiment, if the maximum number of layers is 2, thenthe UE may be configured to use Table 6 or Table 7 or Table 8 for TM9and/or TM10 scheduling for up to 2 layers, thereby enabling dynamicfallback. In another embodiment, if the maximum number of supportedlayers is greater than 2, the UE may be configured to use Table 9 forTM9 and/or TM10 scheduling for up to 4 layers (legacy, or modified table9 as noted above).

It should be noted that, while some embodiments discussed herein referto nodes named eNB and UE, these are merely examples. The eNB may alsobe an access point, base station, node B, gNB, or any other network nodecapable of providing radio access functionality, and the UE may be amobile device, stationary device, IoT device, or any other devicecapable of communication with a wireless or wired communication network.

For 4 MIMO layers, the original table from the 3GPP specifications maybe used or the modified table (as noted in the Tx diversity support forup to 4 layers, e.g., according to Table 9) can be implemented on top ofthe selection depending on the number of supported MIMO layers. Thismay, for example, depend on RRC configuration of an alternative table(e.g., Table 9) for the up to 4 layer MIMO operation.

FIG. 1a illustrates an example flow diagram of a method for dynamicfallback to transmit diversity, according to one embodiment. Forexample, in an embodiment, the method may be for dynamic fallback totransmit diversity with shorter TTI PDSCH TM9 and TM10. In certainembodiments, the flow diagram of FIG. 1a may be performed by a networknode, such as a base station, node B, eNB, gNB, or any other accessnode.

As illustrated in the example of FIG. 1a , the method may optionallyinclude, at 100, receiving a report from a UE of the maximum number ofMIMO layers supported for PDSCH (in general or specifically for shorterTTI). The method may then optionally include, at 110, configuring the UEwith a maximum of 2 MIMO layers for TM9 and/or TM10 (if based on eNBconfiguration) or with the maximum number of MIMO layers reported by theUE. According to certain embodiments, the configuration may be adedicated configuration of maximum MIMO layers (in general orspecifically for shorter TTI), may depend on number of CSI-RS ports(e.g., only two CSI RS ports are configured), and/or may be throughcodebook subset restriction (e.g., UE is configured not to reportrank>2).

In an embodiment, the method may also include, at 120, performing TM9and/or TM10 scheduling. In some embodiments, if the maximum number ofsupported layers is 2, then the performing 120 may include using, orindicating to the UE to use, one of the modified tables providingtransmit diversity fallback according to example embodiments, such asTable 6 or Table 7 or Table 8 for the TM9 and/or TM10 scheduling for upto 2 layers, thereby enabling dynamic fallback. According to some otherembodiments, if the maximum number of supported layers is greater than2, then the performing 120 may include using, or indicating to the UE touse, one of the modified tables providing transmit diversity fallbackaccording to example embodiments, such as Table 9 for TM9 and/or TM10scheduling for up to 4 layers (legacy, or modified table 9 as notedabove).

For example, in some embodiments, the performing 120 may includedetermining if the maximum number of layers is 2. If it is determinedthat the maximum number of layers is 2, then the method may includeusing, or indicating to the UE to use, one of the tables providingtransmit diversity fallback according to example embodiments, such asTable 6 or Table 7 or Table 8 for TM9 and/or TM10 scheduling for up to 2layers, thereby enabling dynamic fallback. If it is determined that themaximum number of supported layers is not 2 (i.e., maximum number oflayers is greater than 2), then the method may include using, orindicating to the UE to use, one of the tables providing transmitdiversity fallback according to example embodiments, such as Table 9 forTM9 and/or TM10 scheduling for up to 4 layers (i.e., legacy tables, ormodified Table 9 providing transmit diversity fallback as noted above).

FIG. 1b illustrates an example flow diagram of a method for dynamicfallback to transmit diversity, according to one embodiment. Forexample, in an embodiment, the method may be for dynamic fallback totransmit diversity with shorter TTI PDSCH TM9 and TM10. In certainembodiments, the flow diagram of FIG. 1b may be performed by a UE,mobile station, mobile equipment, IoT device, or the like.

As illustrated in the example of FIG. 1b , the method may include, at150, reporting the maximum number of downlink shared channel MIMO layers(in general of specifically for shorter TTI) supported to a networknode, for example, based on UE capability signaling. Optionally, in oneembodiment, the method may include, at 160, receiving from the networknode a configuration of a maximum of 2 MIMO layers for TM9 and/or TM10(if based on network configuration). For example, according to someembodiments, the configuration may be a dedicated configuration ofmaximum MIMO layers (in general or specifically for shorter TTI), maydepend on number of CSI-RS antenna ports (e.g., only two CSI RS antennaports are configured), and/or may be through codebook subset restriction(e.g., UE is configured not to report precoding matrix indicescorresponding to rank>2).

According to an embodiment, the method may include determining, at 170,if the maximum number of layers is 2. If it is determined that themaximum number of layers is 2, then the method may include, at 175,using one of the tables providing transmit diversity fallback accordingto example embodiments, such as Table 6 or Table 7 or Table 8 for TM9and/or TM10 scheduling for up to 2 layers, thereby enabling dynamicfallback. If it is determined that the maximum number of supportedlayers is not 2 (i.e., maximum number of layers is greater than 2), thenthe method may include, at 185, using one of the tables for more than 2MIMO layers, such as Table 5 for TM9 and/or TM10 scheduling for up to 4layers (legacy), or modified Table 9 providing transmit diversityfallback according to example embodiments (i.e., legacy tables, ormodified Table 9 providing transmit diversity fallback as noted above).

FIG. 2a illustrates an example of an apparatus 10 according to anembodiment. In an embodiment, apparatus 10 may be a node, host, orserver in a communications network or serving such a network. Forexample, apparatus 10 may be a base station, a Node B, an evolved Node B(eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB),WLAN access point, mobility management entity (MME), and/or subscriptionserver associated with a radio access network, such as a GSM network,LTE network, 5G or NR.

It should be understood that, in some example embodiments, apparatus 10may be comprised of an edge cloud server as a distributed computingsystem where the server and the radio node may be stand-aloneapparatuses communicating with each other via a radio path or via awired connection, or they may be located in a same entity communicatingvia a wired connection. It should be noted that one of ordinary skill inthe art would understand that apparatus 10 may include components orfeatures not shown in FIG. 2 a.

As illustrated in the example of FIG. 2a , apparatus 10 may include aprocessor 12 for processing information and executing instructions oroperations. Processor 12 may be any type of general or specific purposeprocessor. In fact, processor 12 may include one or more ofgeneral-purpose computers, special purpose computers, microprocessors,digital signal processors (DSPs), field-programmable gate arrays(FPGAs), application-specific integrated circuits (ASICs), andprocessors based on a multi-core processor architecture, as examples.While a single processor 12 is shown in FIG. 2a , multiple processorsmay be utilized according to other embodiments. For example, it shouldbe understood that, in certain embodiments, apparatus 10 may include twoor more processors that may form a multiprocessor system (e.g., in thiscase processor 12 may represent a multiprocessor) that may supportmultiprocessing. In certain embodiments, the multiprocessor system maybe tightly coupled or loosely coupled (e.g., to form a computercluster).

Processor 12 may perform functions associated with the operation ofapparatus 10, which may include, for example, precoding of antennagain/phase parameters, encoding and decoding of individual bits forminga communication message, formatting of information, and overall controlof the apparatus 10, including processes related to management ofcommunication resources.

Apparatus 10 may further include or be coupled to a memory 14 (internalor external), which may be coupled to processor 12, for storinginformation and instructions that may be executed by processor 12.Memory 14 may be one or more memories and of any type suitable to thelocal application environment, and may be implemented using any suitablevolatile or nonvolatile data storage technology such as asemiconductor-based memory device, a magnetic memory device and system,an optical memory device and system, fixed memory, and/or removablememory. For example, memory 14 can be comprised of any combination ofrandom access memory (RAM), read only memory (ROM), static storage suchas a magnetic or optical disk, hard disk drive (HDD), or any other typeof non-transitory machine or computer readable media. The instructionsstored in memory 14 may include program instructions or computer programcode that, when executed by processor 12, enable the apparatus 10 toperform tasks as described herein.

In an embodiment, apparatus 10 may further include or be coupled to(internal or external) a drive or port that is configured to accept andread an external computer readable storage medium, such as an opticaldisc, USB drive, flash drive, or any other storage medium. For example,the external computer readable storage medium may store a computerprogram or software for execution by processor 12 and/or apparatus 10.

In some embodiments, apparatus 10 may also include or be coupled to oneor more antennas 15 for transmitting and receiving signals and/or datato and from apparatus 10. Apparatus 10 may further include or be coupledto a transceiver 18 configured to transmit and receive information. Thetransceiver 18 may include, for example, a plurality of radio interfacesthat may be coupled to the antenna(s) 15. The radio interfaces maycorrespond to a plurality of radio access technologies including one ormore of GSM, NB-IoT, LTE, 5G, WLAN, Bluetooth, BT-LE, NFC, radiofrequency identifier (RFID), ultrawideband (UWB), MulteFire, and thelike. The radio interface may include components, such as filters,converters (for example, digital-to-analog converters and the like),mappers, a Fast Fourier Transform (FFT) module, and the like, togenerate symbols for a transmission via one or more downlinks and toreceive symbols (for example, via an uplink).

As such, transceiver 18 may be configured to modulate information on toa carrier waveform for transmission by the antenna(s) 15 and demodulateinformation received via the antenna(s) 15 for further processing byother elements of apparatus 10. In other embodiments, transceiver 18 maybe capable of transmitting and receiving signals or data directly.Additionally or alternatively, in some embodiments, apparatus 10 mayinclude an input and/or output device (I/O device).

In an embodiment, memory 14 may store software modules that providefunctionality when executed by processor 12. The modules may include,for example, an operating system that provides operating systemfunctionality for apparatus 10. The memory may also store one or morefunctional modules, such as an application or program, to provideadditional functionality for apparatus 10. The components of apparatus10 may be implemented in hardware, or as any suitable combination ofhardware and software.

According to some embodiments, processor 12 and memory 14 may beincluded in or may form a part of processing circuitry or controlcircuitry. In addition, in some embodiments, transceiver 18 may beincluded in or may form a part of transceiving circuitry.

As used herein, the term “circuitry” may refer to hardware-onlycircuitry implementations (e.g., analog and/or digital circuitry),combinations of hardware circuits and software, combinations of analogand/or digital hardware circuits with software/firmware, any portions ofhardware processor(s) with software (including digital signalprocessors) that work together to case an apparatus (e.g., apparatus 10)to perform various functions, and/or hardware circuit(s) and/orprocessor(s), or portions thereof, that use software for operation butwhere the software may not be present when it is not needed foroperation. As a further example, as used herein, the term “circuitry”may also cover an implementation of merely a hardware circuit orprocessor (or multiple processors), or portion of a hardware circuit orprocessor, and its accompanying software and/or firmware. The termcircuitry may also cover, for example, a baseband integrated circuit ina server, cellular network node or device, or other computing or networkdevice.

As introduced above, in certain embodiments, apparatus 10 may be anetwork node or RAN node, such as a base station, access point, Node B,eNB, gNB, WLAN access point, or the like. According to certainembodiments, apparatus 10 may be controlled by memory 14 and processor12 to perform the functions associated with any of the embodimentsdescribed herein, such as the flow or signaling diagram illustrated inFIG. 1. For example, in certain embodiments, apparatus 10 may becontrolled by memory 14 and processor 12 to perform one or more of thesteps illustrated in FIG. 1a . In certain embodiments, apparatus 10 maybe configured to perform a procedure for providing dynamic fallback totransmit diversity, for example, with shorter TTI PDSCH TM9 and/or TM10.

For instance, in one embodiment, apparatus 10 may be controlled bymemory 14 and processor 12 to receive a report from a UE of the maximumnumber of MIMO layers supported. In an embodiment, apparatus 10 mayoptionally be controlled by memory 14 and processor 12 to configure theUE with a maximum of 2 MIMO layers for TM9 and/or TM10 (if based on eNBconfiguration) or with the maximum number of MIMO layers reported by theUE. According to certain embodiments, the configuration may be adedicated configuration of maximum MIMO layers (in general orspecifically for shorter TTI), may depend on number of CSI-RS ports(e.g., only two CSI RS ports are configured), and/or may be throughcodebook subset restriction (e.g., UE is configured not to reportrank>2).

In an embodiment, apparatus 10 may be controlled by memory 14 andprocessor 12 to perform TM9 and/or TM10 scheduling. For example, in someembodiments, apparatus 10 may be controlled by memory 14 and processor12 to determine if the maximum number of layers is 2. If it isdetermined that the maximum number of layers is 2, then apparatus 10 maybe controlled by memory 14 and processor 12 to use, or indicate to theUE to use, one of the tables providing transmit diversity fallbackaccording to example embodiments, such as Table 6 or Table 7 or Table 8for TM9 and/or TM10 scheduling for up to 2 layers, thereby enablingdynamic fallback. If it is determined that the maximum number ofsupported layers is not 2 (i.e., maximum number of layers is greaterthan 2), then apparatus 10 may be controlled by memory 14 and processor12 to use, or indicate to the UE to use, one of the tables for more than2 MIMO layers, such as Table 5 for TM9 and/or TM10 scheduling for up to4 layers (legacy) or modified Table 9 providing transmit diversityfallback according to example embodiments (i.e., legacy tables, ormodified Table 9 providing transmit diversity fallback as noted above).

FIG. 2b illustrates an example of an apparatus 20 according to anotherembodiment. In an embodiment, apparatus 20 may be a node or element in acommunications network or associated with such a network, such as a UE,mobile equipment (ME), mobile station, mobile device, stationary device,IoT device, or other device. As described herein, UE may alternativelybe referred to as, for example, a mobile station, mobile equipment,mobile unit, mobile device, user device, subscriber station, wirelessterminal, tablet, smart phone, IoT device or NB-IoT device, or the like.As one example, apparatus 20 may be implemented in, for instance, awireless handheld device, a wireless plug-in accessory, or the like.

In some example embodiments, apparatus 20 may include one or moreprocessors, one or more computer-readable storage medium (for example,memory, storage, or the like), one or more radio access components (forexample, a modem, a transceiver, or the like), and/or a user interface.In some embodiments, apparatus 20 may be configured to operate using oneor more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G,WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and/or any other radioaccess technologies. It should be noted that one of ordinary skill inthe art would understand that apparatus 20 may include components orfeatures not shown in FIG. 2 b.

As illustrated in the example of FIG. 2b , apparatus 20 may include orbe coupled to a processor 22 for processing information and executinginstructions or operations. Processor 22 may be any type of general orspecific purpose processor. In fact, processor 22 may include one ormore of general-purpose computers, special purpose computers,microprocessors, digital signal processors (DSPs), field-programmablegate arrays (FPGAs), application-specific integrated circuits (ASICs),and processors based on a multi-core processor architecture, asexamples. While a single processor 22 is shown in FIG. 2b , multipleprocessors may be utilized according to other embodiments. For example,it should be understood that, in certain embodiments, apparatus 20 mayinclude two or more processors that may form a multiprocessor system(e.g., in this case processor 22 may represent a multiprocessor) thatmay support multiprocessing. In certain embodiments, the multiprocessorsystem may be tightly coupled or loosely coupled (e.g., to form acomputer cluster).

Processor 22 may perform functions associated with the operation ofapparatus 20 including, as some examples, precoding of antennagain/phase parameters, encoding and decoding of individual bits forminga communication message, formatting of information, and overall controlof the apparatus 20, including processes related to management ofcommunication resources.

Apparatus 20 may further include or be coupled to a memory 24 (internalor external), which may be coupled to processor 22, for storinginformation and instructions that may be executed by processor 22.Memory 24 may be one or more memories and of any type suitable to thelocal application environment, and may be implemented using any suitablevolatile or nonvolatile data storage technology such as asemiconductor-based memory device, a magnetic memory device and system,an optical memory device and system, fixed memory, and/or removablememory. For example, memory 24 can be comprised of any combination ofrandom access memory (RAM), read only memory (ROM), static storage suchas a magnetic or optical disk, hard disk drive (HDD), or any other typeof non-transitory machine or computer readable media. The instructionsstored in memory 24 may include program instructions or computer programcode that, when executed by processor 22, enable the apparatus 20 toperform tasks as described herein.

In an embodiment, apparatus 20 may further include or be coupled to(internal or external) a drive or port that is configured to accept andread an external computer readable storage medium, such as an opticaldisc, USB drive, flash drive, or any other storage medium. For example,the external computer readable storage medium may store a computerprogram or software for execution by processor 22 and/or apparatus 20.

In some embodiments, apparatus 20 may also include or be coupled to oneor more antennas 25 for receiving a downlink signal and for transmittingvia an uplink from apparatus 20. Apparatus 20 may further include atransceiver 28 configured to transmit and receive information. Thetransceiver 28 may also include a radio interface (e.g., a modem)coupled to the antenna 25. The radio interface may correspond to aplurality of radio access technologies including one or more of GSM,LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, andthe like. The radio interface may include other components, such asfilters, converters (for example, digital-to-analog converters and thelike), symbol demappers, signal shaping components, an Inverse FastFourier Transform (IFFT) module, and the like, to process symbols, suchas OFDMA symbols, carried by a downlink or an uplink.

For instance, transceiver 28 may be configured to modulate informationon to a carrier waveform for transmission by the antenna(s) 25 anddemodulate information received via the antenna(s) 25 for furtherprocessing by other elements of apparatus 20. In other embodiments,transceiver 28 may be capable of transmitting and receiving signals ordata directly. Additionally or alternatively, in some embodiments,apparatus 10 may include an input and/or output device (I/O device). Incertain embodiments, apparatus 20 may further include a user interface,such as a graphical user interface or touchscreen.

In an embodiment, memory 24 stores software modules that providefunctionality when executed by processor 22. The modules may include,for example, an operating system that provides operating systemfunctionality for apparatus 20. The memory may also store one or morefunctional modules, such as an application or program, to provideadditional functionality for apparatus 20. The components of apparatus20 may be implemented in hardware, or as any suitable combination ofhardware and software. According to an example embodiment, apparatus 20may optionally be configured to communicate with apparatus 10 via awireless or wired communications link 70 according to any radio accesstechnology, such as NR.

According to some embodiments, processor 22 and memory 24 may beincluded in or may form a part of processing circuitry or controlcircuitry. In addition, in some embodiments, transceiver 28 may beincluded in or may form a part of transceiving circuitry.

As discussed above, according to some embodiments, apparatus 20 may be aUE, mobile device, mobile station, ME, IoT device and/or NB-IoT device,for example. According to certain embodiments, apparatus 20 may becontrolled by memory 24 and processor 22 to perform the functionsassociated with example embodiments described herein. For example, insome embodiments, apparatus 20 may be configured to perform one or moreof the processes depicted in any of the flow charts or signalingdiagrams described herein, such as the flow diagrams illustrated in FIG.1 b.

According to some embodiments, apparatus 20 may be controlled by memory24 and processor 22 to report the maximum number of MIMO layerssupported by apparatus 20 to a network node, for example, based on UEcapability signaling. The maximum number of MIMO layers may begenerically applicable or specifically for shorter TTI operation.Optionally, in one embodiment, apparatus 20 may be controlled by memory24 and processor 22 to receive from the network node a configuration ofa maximum of 2 MIMO layers for TM9 and/or TM10 (if based on networkconfiguration). For example, according to some embodiments, theconfiguration may be a dedicated configuration of maximum MIMO layers(in general or specifically for shorter TTI), may depend on number ofCSI-RS ports (e.g., only two CSI RS ports are configured), and/or may bethrough codebook subset restriction (in general or specifically forshorter TTI, e.g., UE is configured not to report rank>2).

According to an embodiment, apparatus 20 may be controlled by memory 24and processor 22 to determine if the maximum number of layers is 2. Ifit is determined that the maximum number of layers is 2, then apparatus20 may be controlled by memory 24 and processor 22 to use one of thetables providing transmit diversity fallback according to exampleembodiments, such as Table 6 or Table 7 or Table 8 for TM9 and/or TM10scheduling for up to 2 layers, thereby enabling dynamic fallback. If itis determined that the maximum number of layers is not equal to 2 (i.e.,more than 2 MIMO layers are supported), then apparatus 20 may becontrolled by memory 24 and processor 22 to use one of the tables formore than 2 MIMO layers, such as Table 5 for TM9 and/or TM10 schedulingfor up to 4 layers (legacy), or modified table 9 providing transmitdiversity fallback (as noted above).

Therefore, certain example embodiments provide several technicalimprovements, enhancements, and/or advantages. Various exampleembodiments may provide support for dynamic transmit diversity fallbackfor TM9/TM10. For up to 2 layer MIMO support, example embodiments enabledynamic diversity fallback without any additional drawbacks (as onlynon-useable entries in mapping tables are utilized). As such, exampleembodiments can improve performance, latency, and/or throughput ofnetworks and network nodes including, for example, access points, basestations/eNBs/gNBs, and mobile devices or UEs. Accordingly, the use ofcertain example embodiments result in improved functioning ofcommunications networks and their nodes.

In some example embodiments, the functionality of any of the methods,processes, signaling diagrams, algorithms or flow charts describedherein may be implemented by software and/or computer program code orportions of code stored in memory or other computer readable or tangiblemedia, and executed by a processor.

In some example embodiments, an apparatus may be included or beassociated with at least one software application, module, unit orentity configured as arithmetic operation(s), or as a program orportions of it (including an added or updated software routine),executed by at least one operation processor. Programs, also calledprogram products or computer programs, including software routines,applets and macros, may be stored in any apparatus-readable data storagemedium and include program instructions to perform particular tasks.

A computer program product may comprise one or more computer-executablecomponents which, when the program is run, are configured to carry outsome example embodiments. The one or more computer-executable componentsmay be at least one software code or portions of it. Modifications andconfigurations required for implementing functionality of an embodimentmay be performed as routine(s), which may be implemented as added orupdated software routine(s). Software routine(s) may be downloaded intothe apparatus.

Software or a computer program code or portions of it may be in a sourcecode form, object code form, or in some intermediate form, and it may bestored in some sort of carrier, distribution medium, or computerreadable medium, which may be any entity or device capable of carryingthe program. Such carriers include a record medium, computer memory,read-only memory, photoelectrical and/or electrical carrier signal,telecommunications signal, and software distribution package, forexample. Depending on the processing power needed, the computer programmay be executed in a single electronic digital computer or it may bedistributed amongst a number of computers. The computer readable mediumor computer readable storage medium may be a non-transitory medium.

In other example embodiments, the functionality may be performed byhardware or circuitry included in an apparatus (e.g., apparatus 10 orapparatus 20), for example through the use of an application specificintegrated circuit (ASIC), a programmable gate array (PGA), a fieldprogrammable gate array (FPGA), or any other combination of hardware andsoftware. In yet another example embodiment, the functionality may beimplemented as a signal, a non-tangible means that can be carried by anelectromagnetic signal downloaded from the Internet or other network.

According to an embodiment, an apparatus, such as a node, device, or acorresponding component, may be configured as circuitry, a computer or amicroprocessor, such as single-chip computer element, or as a chipset,including at least a memory for providing storage capacity used forarithmetic operation and an operation processor for executing thearithmetic operation.

One having ordinary skill in the art will readily understand that theexample embodiments as discussed above may be practiced with steps in adifferent order, and/or with hardware elements in configurations whichare different than those which are disclosed. Therefore, although someembodiments have been described based upon these example preferredembodiments, it would be apparent to those of skill in the art thatcertain modifications, variations, and alternative constructions wouldbe apparent, while remaining within the spirit and scope of exampleembodiments.

We claim:
 1. An apparatus, comprising: at least one processor; and atleast one memory comprising computer program code, the at least onememory and computer program code configured, with the at least oneprocessor, to cause the apparatus at least to configure a user equipmentwith a maximum number of multiple-input multiple-output layers used fortransmission mode 9 or transmission mode 10 scheduling; perform at leastone of transmission mode 9 or transmission mode 10 scheduling, whereinthe configuring comprises indicating to the user equipment to use amodified mapping table providing transmit diversity fallback for the atleast one of transmission mode 9 or transmission mode 10 scheduling,wherein, when a maximum number of multiple-input multiple-output layerssupported for a physical downlink shared channel is 2, the at least onememory and computer program code are configured, with the at least oneprocessor, to cause the apparatus at least to indicate to the userequipment to use at least one modified mapping table providing transmitdiversity fallback for the at least one of transmission mode 9 ortransmission mode 10 scheduling for up to 2 layers, and wherein, when amaximum number of multiple-input multiple-output layers supported forthe physical downlink shared channel is greater than 2, the at least onememory and computer program code are configured, with the at least oneprocessor, to cause the apparatus at least to indicate to the userequipment to use at least one modified mapping table providing transmitdiversity fallback for the at least one of transmission mode 9 ortransmission mode 10 scheduling for up to 4 layers.
 2. The apparatusaccording to claim 1, wherein, when the maximum number of multiple-inputmultiple-output layers supported for the physical downlink sharedchannel is 2, the at least one modified mapping table differs from anon-modified table by replacing at least entries in the non-modifiedtable for 3-layer and 4-layer transmission with 2-layer transmissiondiversity fallback entries.
 3. The apparatus according to claim 1,wherein, when the maximum number of multiple-input multiple-outputlayers supported for the physical downlink shared channel is greaterthan 2, the at least one modified mapping table differs from anon-modified table by replacing at least one entry in the non-modifiedtable for 2-layer spatial multiplexing transmission with a 2-layertransmission diversity fallback entry.
 4. The apparatus according toclaim 1, wherein the at least one memory and computer program code areconfigured, with the at least one processor, to cause the apparatus atleast to receive a report from the user equipment of the maximum numberof multiple-input multiple-output layers supported for the physicaldownlink shared channel.
 5. The apparatus according to claim 1, whereinthe configuring comprises a dedicated configuration of maximummultiple-input multiple-output layers, or wherein the configuringdepends on number of channel station information reference signal ports,or the configuring is performed through codebook subset restriction. 6.A method, comprising: receiving, from a network node, a configuration ofa maximum number of multiple-input multiple-output layers used fortransmission mode 9 or transmission mode 10 scheduling; using, based onthe received configuration, a modified mapping table providing transmitdiversity fallback for at least one of transmission mode 9 ortransmission mode 10 downlink shared channel reception, wherein, when amaximum number of multiple-input multiple-output layers supported for aphysical downlink shared channel is 2, the using further comprises usingat least one modified mapping table providing transmit diversityfallback for the at least one of transmission mode 9 or transmissionmode 10 scheduling for up to 2 layers, and wherein, when a maximumnumber of multiple-input multiple-output layers supported for thephysical downlink shared channel is greater than 2, the using furthercomprises using at least one modified mapping table providing transmitdiversity fallback for the at least one of transmission mode 9 ortransmission mode 10 scheduling for up to 4 layers.
 7. The methodaccording to claim 6, wherein, when the maximum number of multiple-inputmultiple-output layers supported for the physical downlink sharedchannel is 2, the at least one modified mapping table differs from anon-modified table by replacing at least the entries in the non-modifiedmapping table for 3-layer and 4-layer transmission with 2-layertransmission diversity fallback entries.
 8. The method according toclaim 6, wherein, when the maximum number of multiple-inputmultiple-output layers supported for the physical downlink sharedchannel is greater than 2, the at least one modified mapping tablediffers from a non-modified table by replacing at least the entries inthe non-modified table for 3-layer and 4-layer transmission with 2-layertransmission diversity fallback entries.
 9. The method according toclaim 6, further comprising reporting, to a network node, a maximumnumber of downlink shared channel multiple-input multiple-output layersthat are supported.
 10. The method according to claim 6, wherein theconfiguration comprises a dedicated configuration of maximummultiple-input multiple-output (MIMO) layers, or wherein theconfiguration depends on number of channel station information referencesignal ports, or the configuration is performed through codebook subsetrestriction.
 11. An apparatus, comprising: at least one processor; andat least one memory comprising computer program code, the at least onememory and computer program code configured, with the at least oneprocessor, to cause the apparatus at least to receive, from a networknode, a configuration of a maximum number of multiple-inputmultiple-output layers used for transmission mode 9 or transmission mode10 scheduling; use, based on the received configuration, a modifiedmapping table providing transmit diversity fallback for at least one oftransmission mode 9 or transmission mode 10 downlink shared channelreception, wherein, when a maximum number of multiple-inputmultiple-output layers supported for a physical downlink shared channelis 2, the at least one memory and computer program code are configured,with the at least one processor, to cause the apparatus at least to useat least one modified mapping table providing transmit diversityfallback for the at least one of transmission mode 9 or transmissionmode 10 scheduling for up to 2 layers, and wherein, when a maximumnumber of multiple-input multiple-output layers supported for thephysical downlink shared channel is greater than 2, the at least onememory and computer program code are configured, with the at least oneprocessor, to cause the apparatus at least to use at least one modifiedmapping table providing transmit diversity fallback for the at least oneof transmission mode 9 or transmission mode 10 scheduling for up to 4layers.
 12. The apparatus according to claim 11, wherein, when themaximum number of multiple-input multiple-output layers supported forthe physical downlink shared channel is 2, the at least one modifiedmapping table differs from a non-modified table by replacing at leastthe entries in the non-modified mapping table for 3-layer and 4-layertransmission with 2-layer transmission diversity fallback entries. 13.The apparatus according to claim 11, wherein, when the maximum number ofmultiple-input multiple-output layers supported for the physicaldownlink shared channel is greater than 2, the at least one modifiedmapping table differs from a non-modified table by replacing at leastthe entries in the non-modified table for 3-layer and 4-layertransmission with 2-layer transmission diversity fallback entries. 14.The apparatus according to claim 11, wherein the at least one memory andcomputer program code are configured, with the at least one processor,to cause the apparatus at least to report, to a network node, a maximumnumber of downlink shared channel multiple-input multiple-output layersthat are supported.
 15. The apparatus according to claim 11, wherein theconfiguration comprises a dedicated configuration of maximummultiple-input multiple-output layers, or wherein the configurationdepends on number of channel station information reference signal ports,or the configuration is performed through codebook subset restriction.16. A non-transitory computer readable medium comprising programinstructions which, when executed by a processor, cause the processor toperform at least the method according to claim 6.